What is the normal range?

[photocopier]

I have had a recent Thyroid blood test, but still do not understand what the normal thyroid ranges are? I have an underactive thyroid that was going into hashimoto's but now been told it's normal. I'm on thyroxine and want to get off it. Does anyone have any advice please

[jimh111]

The reference interval ('normal range' is incorrect) is a statistical interval in which approximaely 95% of a presumed healthy population lie. So for each hormone it's the interval in which 95% of healthy people are. e.g. 95% of healthy people will have an fT3 between 3.5 and 6.5.

The reference interval is not a diagnostic range, if it was by definition 5% of the healthy population would be unhealthy! i.e. 2.5% would be below the lower limit and 2.5% above the upper limit. Unfortunately, doctors tend to treat reference intervals as diagnostic ranges, they are not.

Neither are reference intervals therapeutic targets, there's no guarantee that if you bring e.g. TSH into its reference interval the patient will become perfectly well.

Of course if a patient has e.g a TSH outside its reference interval there is an increased chance that they are ill, because their levels are unusual. This can be very reliable, patients with say, a TSH > 20 will almost certainly have a failing thyroid gland. On the other hand patients with a perfectly normal TSH of say, 1.5 may also be hypothyroid. The blood tests assist diagnosis but signs, symptoms and response to treatment are more important. Unfortunately, doctors have become lazy and will tend to diagnose and treat according to numbers rather than the patients condition.

These are the reasons why I never used the term 'normal range', it gives an importance to a statistical object that it should not have.

In your case you should ask for a copy of the results, the reference interval is very wide and your actual result has a large bearing when it comes to treating hypothyroidism. Another complication is that if you have Hashimoto's your thyroid can be irratic in its output until if finally packs in, making you levels jump up and down. Whether you can come off thyroid hormone, levothyroxine in your case, will depend on whether your thyroid have a temporary problem (can happen, e.g. after childbirth) or is in permanent decline which is much more common.

[MaisieGray]

There are no 'normal' ranges, only the ranges used by each individual laboratory doing the testing. Hence ranges can vary from lab to lab so that whenever you post blood test results for members to comment on, it is important that you provide both the result and the actual range given by the lab.

An underactive thyroid cannot "go into Hashimoto's". Someone can develop autoimmune thyroiditis aka Hashimoto's which over time can attack and destroy the thyroid in most, but not all cases, leading to hypothyroidism - some people test positive for the antibodies and never develop hypothyroidism, but generally they do. Other people, such as myself, can develop non-autoimmune hypothyroidism and not know the reason. But the state of having an under-active thyroid, can't itself morph into Hashimoto's.

Generally, if you have a dysfunctional thyroid for whatever reason, it will be for life. There are certain situations where people can experience temporary problems such as after pregnancy, miscarriage, a viral infection and a bacterial infection being some, although even with those, a largish percentage will develop permanent hypothyroidism. So generally you will be taking exogenous thyroid hormones for life. The only way to comment on your particular situation is if you post the blood test results you had that led to your diagnosis and treatment, and your most recent results that led you to being told you are in fact, euthyroid ie don't have a thyroid problem. If you don't have the results and their ranges, you can ask at your surgery's reception for copies to be printed off for you, which you are entitled to by law. Then you can post them and ask for members' comments. Without knowing those results, it won't be possible to help you, it would simply be guesswork.

[Wendy22]

Every lab has different ranges.

NICE guidlines state TSH should be bottom half of lab range normally below 2.5 Once on levothyroxine.

You would be best getting a print out of your blood results

[MaisieGray in reply to Wendy22]

Not wishing to be pedantic, but for accuracy sake, it isn't that every lab has different ranges. A lab may differ one from the next, but equally may be the same as another - for any assay, a laboratory can develop and use its own range, but may choose instead, to use the manufacturer’s ranges, published reference ranges, or locally established ranges as the baseline, so there can easily be overlap/the same ranges used by numerous labs. Regarding NICE Guidelines, they aren't yet published, but the Clinical Knowledge Summary states that when treating sub-clinical hypothyroidism, Drs should aim (in most people) to reach a stable TSH level in the lower half of the reference range (0.4–2.5 mU/L). However, in cases of overt hypothyroidism, it states less specifically that treatment should aim to normalize serum TSH and improve thyroid hormone concentrations to the euthyroid state.

[greygoose]

I have an underactive thyroid that was going into hashimoto's but now been told it's normal.

That statement is rather ambiguous, I'm afraid, and I'd rather like to know exactly what you mean.

Maisie has explained that you can't 'go into' Hashi's - you either have it or you don't. But, what have you been told is now normal? The Hashi's?

Are you saying that on one test you had over-range antibodies, but now they're back in-range again - i.e. normal? If so, whoever told you that doesn't know what he's talking about.

Antibodies fluctuate all the time. They can be over-range on one test, then in-range on the next. But, if you've once ever had an over-range result, it means you have Hashi's. And Hashi's doesn't go away. Even if the level goes down again, you still have Hashi's, because the antibodies are not the disease, they are an indication of the disease. And their fluctuation doesn't actually mean anything. You either have it or you don't.

And, it rather sounds like you do. So, the chances of you being able to come off levo are more than likely non-existant. You need it to live. And, if your thyroid has been damaged by the Hashi's, your thyroid will never again be able to make enough hormone to keep you healthy.

But, as Maisie said, we really need to see your blood test results to understand exactly what is going on.

[SlowDragon Administrator]

If you have Hashimoto's, it's extremely unlikely you would be able to stop taking Levothyroxine

Levothyroxine is not a medicine, it's a replacement thyroid hormone as your body no longer makes enough

Just like a diabetic needs insulin a hypothyroid patient needs replacement thyroid hormones

If you don't feel fully well then this suggests your not correctly treated

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if Thyroid antibodies are raised

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water . This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Last Levothyroxine dose should be 24 hours prior to test, (taking delayed dose immediately after blood draw).

Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or all vitamins

thyroiduk.org.uk/tuk/testin...

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random